A powertrain can propel a vehicle and may include an internal combustion engine and an intake manifold in fluid communication with the internal combustion engine. The internal combustion engine has at least one cylinder and can receive air from the intake manifold. Then, the internal combustion engine can combust an air/fuel mixture in the cylinders in order to generate output torque. An intake valve controls the airflow to the cylinders. Specifically, the intake valve can open and close at specific times to either allow air to enter the cylinders or preclude air from the entering the cylinders. The internal combustion engine may be a homogenous charge compression ignition (HCCI) engine. In an HCCI engine, an air/fuel mixture is compressed to the point of auto-ignition.